1. Field of the Invention
The present invention generally relates to semiconductor devices and supporting plates, and more particularly, to a semiconductor device having a resin substrate where a conductive element is mounted and a supporting plate.
2. Description of the Related Art
A BGA (Ball Grid Array) package or an LGA (Land Grid Array) package, for example, has a structure wherein a semiconductor element is mounted on an upper surface of a resin substrate and an external connection terminal such as a solder ball or a land is provided on a lower surface of the resin substrate.
FIG. 1 is a front view of a related art semiconductor device 10, and FIG. 2 is a plan view of the semiconductor device 10. For the convenience of explanation, a cross section of a stiffener 14 is shown in FIG. 1.
The semiconductor device 10 shown in FIG. 1 and FIG. 2 has a BGA package structure. In the semiconductor device 10, a semiconductor element 11 is mounted on the center of an upper surface of a resin substrate 12. Plural solder balls 13 as external connection terminals are provided on a lower surface of the resin substrate 12. In the example shown in FIG. 1 and FIG. 2, the semiconductor element 11 is flip-chip connected to the resin substrate 12.
The resin substrate 12 is formed as a multilayer wiring substrate. More specifically, the resin substrate 12 has a structure where wiring layers, via forming part interfacially connecting the wiring layers, and others are formed in a base material made of an organic resin material. The semiconductor element 11 and the solder balls 13 are electrically connected to each other by the wiring layer formed in the resin substrate 12 and the via forming parts.
In the meantime, the semiconductor device 10 may be mounted on a mounting substrate in a state where the semiconductor device 10 is installed in a BGA socket. In this case, if a deformation such as a curve or bending happens to the resin substrate 12, all of the solder balls 3 may not be connected to an electrode of the socket. Because of this, a high co-planarity (flatness) is required of the resin substrate 12.
In addition, when the semiconductor element 11 is flip-chip connected to the resin substrate 12 as described above, if the deformation such as the curve or bending happens to the resin substrate 12, plural bumps (not shown in FIG. 1 and FIG. 2) formed in the semiconductor element 11 may not be connected to the resin substrate 12.
The stiffener 14 is provided at the resin substrate 12 to solve the above-mentioned problems. As shown in FIG. 2, the stiffener 14 has an area having a substantially same size as the resin substrate 12. An opening part 16 is formed in the center of the stiffener 14 so that the semiconductor element 11 can be mounted on the resin substrate 12 in the opening part 16.
The stiffener 14 is a member having a plate-shaped configuration and formed by a metal material. The stiffener 14 is adhered to the resin substrate 12 by using a resin adhesive 15. Accordingly, the resin substrate 12 is supported by the stiffener 14 and thereby co-planarity (flatness) can be maintained.
However, recently and continuing, the number of pins is increasing as the semiconductor elements 11 are provided with higher densities. Therefore, the number of the external connection terminals (solder balls 13) is also increasing. In addition, as the number of the external connection terminals is increasing, the size of the package (resin substrate 12) is becoming larger. Thus, as the size of the semiconductor device 10 becomes larger, the size of the stiffener 14 becomes large so that an adhesive area of the resin substrate 12 and the stiffener 14 is increasing.
On the other hand, since the resin substrate 12 is made of the organic resin material, some degree of moisture absorption is generated. In addition, similarly, since the resin adhesive 15 is made of the organic resin, some degree of moisture absorption is generated. The absorbed moisture is vaporized and gasified by a heating process implemented when the solder ball 13 is mounted on the mounting substrate. When the absorbed moisture is gasified, a large amount of a volumetric expansion may occur.
In a case where the number of the external connection terminals is small and therefore configurations of the resin substrate 12 and the stiffener 14 are small, the generated gas can escape to a side of a periphery of the stiffener 14 or a side of the opening part 16. However, in a case where the size of the stiffener 14 becomes large as the size of the semiconductor device 10 becomes larger, so that the adhesive area of the resin substrate 12 and the stiffener 14 is increasing, there is no path for the escape of the generated gas.
Therefore, there are problems in the related art that damage such as inter layer peeling or disconnection may be generated in the resin substrate 12 and peeling may be generated at a connection part between the resin substrate 12 and the stiffener 14, and therefore reliability of the semiconductor device 10 is decreased.